Living in a hi-tech militarised age, unexpected attacks from unknown sources warrant responses that are also hi-tech. In this world of bombs and explosives, it is imperative to know where they are stashed away.

A sensor that precisely detects the presence of explosives has been developed recently by IISc as part of its efforts in improving national security. The sensor has been developed by physics professor A K Sood and organic chemistry professor N Jayaraman.

The sensor, Prof Sood says, is built in the mode of a sniffer. The sensor has properties that detect vapour from TNT or other form of explosives. Once the vapour is detected, the fluorescence inside the sensor shuts off.

The shutting off is the indicator that there are explosives in the vicinity. Fluorescents on other sensors may stay put, while in this particular sensor the light fades out. But catching the vapour is vital, which is the first sign of explosives being in the vicinity.

If the quantity of explosives is large, the sensor detects the same from a distance. If the quantity is small, it would have to be closer to the haul. Fluorescence, a form of luminescence, has many practical applications, including mineralogy, gemology, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors, and, most commonly, fluorescent lamps.

â€œThe sensor was developed after a yearâ€™s research. We tested it in the lab where it demonstrated its detecting capabilities,â€ Prof Sood said.

â€œThe forthcoming tests will be real-time and deepening on its operations, it will be commercialised and used real-time. The sensor is almost on a nanoscale and will be fitted into a larger device when it comes out as a product. The unique feature of this sensor is that it is ultra-sensitive, much more than existing sensors,â€ he added.

Due to the low volatility of explosives, absorptive materials such as polymers have been employed as explosive vapour sensors. While monitoring these vapours, they accumulate over the sensing element of the detectors through condensation.

Once a certain mass threshold of vapours has been achieved depending on the type of analyte present, detection occurs. (Analyte is a substance or chemical constituent that is of interest in an analytical procedure).

Nanotechnology-enabled sensors have advantages over conventional sensors. They have better sensitivity and selectivity, low production costs, reduced power consumption and fairly good stability.

The properties of nanoscale materials such as increased surface area make them ideal for sensing.

New devices

Nanomaterials can be incubated into existing sensing technologies or can be used to develop new devices.

Various types of sensors such as physical sensors, electro-sensors, chemical sensors and biosensors, have greatly benefited from nanotechnology.

Scientists Sarah J Toal and William C Trogler from the US wrote in the â€˜Journal of Materials Chemistryâ€™ that chemical sensors for the rapid detection of explosives are important because they have important applications, such as tactical and humanitarian demining, remediation of explosives manufacturing sites and forensic and criminal investigations.